I just bought a 1968 Mercury 1250 outboard that I had hoped to get running. But my first problem is that the previous owner cut all the wire harness wires off the key switch and I have no idea how to rewire the switch. I have a manual but it doesnt show me how to accomplish this. So far I have the red wire to the battery post, the black wire to the ground and the yellow wire to the solenoid. Now I have 4 wires left (salmon,grey,brown and white) with no idea where to put them. Any help would be a HUGE help and probably a miracle as the boat stores in my town cant even help

Wow!!! I cannot help with that but do you have any pictures of the boat?

Somebody on here may be able to assist you, though. Pictures of the harness and helm would also help in this regard.

Welcome to the board.

What kind of switch do you have,

Three position, OFF-ON-IGN
Four position, OFF-ACC-ON-IGN
Or either of those with push choke

That would help in determining where the spaghetti goes.

Not much help here either, but as alluded to above, some wires may be for accessories such as the radio so may not be important for starting and keeping the engine running.

The new key switch is Three position, OFF-ON-IGN pictures wouldnt do any good as the key switch is not installled on the boat. Right now I am just trying to see if this motor will start before I put too much money into it. The starter will crank it over by running the battery directly to the starter but I do believe that I need all the wires connected before it will actually start. ALl of these wires go into the motor, none are accesories.This is what I DO know, 3 of these wires go to the switch box, 1 to the choke and the other 3 go to the starter solenoid. My switch lists the posts as mag,mag,sol,bat,acc,grd. So now maybe you see my problem. The posts dont seem to match the wires in any way that I can figure out.

Yeah you need to wire through the nuetral safety switch at the control stick.

Pictures are worth a thousand words.

OK it seems I have not made myself very clear. I have the outboard on a stand with the wiring harness laying on the ground. I bought a key switch and I am trying to hook up the important wires to see if this motor will start. There is no boat,no acc, no control stick and no neutral start switch. if you would like to see a picture of a wiring harness that is probably doable but all it is is 7 wires coming out of the motor going to the key switch. Does anyone happen to know where they connect on the key switch and which ones I NEED in order for the motor to run.Thank you

Does the manual you have show ANY wiring diagrams? If so, maybe you could post the wiring diagrams here and we can help you decipher them.

If you have a three position switch, you probably have three poles off the back, correct? i noticed once when i pulled a switch that the housing was a somewhat generic housing and had all the post positions labeled, but only had posts on three of them. I hope I said that non-cofusingly.

First of all, I don't think all 7 wires go to your switch. You'll have a power to your switch (typically your BAT position), you should have a power going to your starter from your battery as this will feed the starter, but the IGN from your switch should go the starter solenoid/relay as your switch can not handle the starter in rush and current. One of those wires as you stated is for the choke. The wire from the ON position of the switch should go to supply power to the ignition system of the boat for powering the coil and such.

I would say the request for the wiring diagram if so available would help greatly.

How about this wiring diagram?






http://www.maxrules.com/oldmercs/Wiring/1966ona/32.pdf

According to this diagram, and assuming that all of the stuff shown on this diagram is in existence on your engine (except for the Remote Control), then this is true for the key switch (your key switch probably has different terminal letters than this):

OFF D-E (black connects to salmon)

RUN A-F (red connects to white)

START A-F-B (red and white and yellow are connected)


For your unused wires:

salmon - connects to key switch, but is not carried through the engine harness plug

brown - goes to the tachometer connection on the remote control

white and grey - involved in the chock switch (white is also used on the key switch)

yes I have that diagram. And you are correct , the salmon wire does not go through to the engine harness(which is also confusing, why does it just stop at the plug?) Anyway, you have touched on the problem here. the letters on the back of the key switch are NOT labled like this so WHERE do I connect each wire to? As I stated earlier, my new key switch has 6 posts and they are labled like this.. mag, sol, grnd, mag, acc, bat,

This is 1 major part I cannot figure out, which color wire powers the coil as no wire goes directly to the coil. As I stated earlier 3 wires go to the switch box assy and from there one goes to the coil so I have no idea which powers it. This is all very confusing. You would think that there would be a basic diagram stating which color wire goes on which post of the key switch

Let's start with some basics. (Warning: I've never worked on an outboard engine of any sort. All of the following is from reading and deciphering the wiring diagram. My advice is only worth what you've paid for it.)

I'm assuming that you have the male/female connector that connects the engine harness to the external harness? If so, do the colors and number of wires match that of the wiring diagram I posted? We should have the following:

Engine Harness Connector:
"A" Red (2 wires; 1 to switch box and 1 to starter solenoid)
"B" Yellow (to starter solenoid)
"C" Gray (to choke)
"D" Black (to ground - maybe to starter solenoid also?)
"F" White (to switch box)
"G" Brown (to switch box)

External Harness Connector
"A" Red
"B" Yellow
"C" Gray
"D" Black
"E" Salmon
"F" White
"G" Brown


The letters shown above should match up with markings on the engine/external harness connectors. Notice that the colors do not match up exactly on both sides of this connector. Namely the salmon wire on the external harness does not have a corresponding wire on the engine harness. And the engine harness side has two red wires, whereas the external harness side has only one red wire.

Now if all of the above checks out EXACTLY, then we can go to the next step. If ANYTHING doesn't match up as listed above, then we need to iron that out before doing anything else.

And right off from your first post I can see a problem. You said:

You have the black and red wires hooked up correctly, but the yellow wire on the external harness side does not go to the solenoid. The yellow wire on the engine harness side should already be connected to the solenoid. So go ahead and disconnect the yellow wire that you had connected.

I'm hoping you have an electrical meter of some sort that you can use to test your new key switch. The electrical meter doesn't have to be very fancy - all we're going to be checking is electrical continuity between different terminals while the switch is in the three different positions. What I need you to do is determine which terminals are connected to one another at the OFF position, at the ON position, and at the IGN position, and then post that information here.

We'll get this thing sorted out once and for all !!

One of the problems with wiring diagrams is figuring out what to ignore...




========
You mention "why does it just stop at the plug?" --- Note in the diagram above I've circled two parts---these 2 parts are the 2 halves of the main connector plug, so they're virtually the same thing. You only need to concern yourself with the side that goes to the ignition switch, choke switch, neutral switch and tachometer. Everything else in the diagram is "done", and is just confusing.

Below is all the wiring diagram you need for the ignition switch connection:

FR,

Good points you make.

I was trying to make sure that this diagram really reflects the engine that he has. You don't want to know the bad times I've had using the wrong wiring diagram and not realizing it for several hours (or days). I tend to say bad words then.

By the way, do you know what the three wires to the tachometer do? (other than show engine rpms's, of course)

And do you know what is inside outboard "switch boxes". I did a Google search last night on this subject and found remarkably little.

From what I can see---

The switchbox isn't much more than a central junction box, doesn't look like it does much else...

The mercury switch opens the brown 'trigger' circuit to the distributor if the engine is upside down, failsafe in case the boat capsizes. The brown trigger wire also "tells" the tach how fast the engine is going, the tach counts the trigger pulses from the distributor.

The white wire is HOT when the ignition switch is ON, it's fed from the switchbox, and powers the choke button and distributor.

The Yellow wire is HOT when the ignition switch is in START position, feeds the starter solenoid. The AC wires from the stator are yellow also. The rectifier changes AC current from the stator to DC current.

The gray wire is HOT (fed from the white) when the choke button is pushed, to activate the choke solenoid.

The Black is ground, as usual...

Red is battery, always HOT.

The salmon wire goes absolutely nowhere after it reaches the connector from the switch, I can only assume it's for a different motor diagram (so why is it still included?)

What puzzles me is the coil wiring, the lower wire is marked 'black ground', so I guess the upper unmarked black wire must be hot?

ANYWAY-- To be able to start the engine, everything must be connected as shown, I don't see any shortcuts...

FR,

Thanks for the info on how the tachometer works. I guess the white and black wires are for power, and the brown wire is for signal?



There must be more inside of the "switch box" than just connections. I've seen replacement "switch boxes" on the Internet go for $150 on up. And this site shows a "switch box" for the 1250 as costing $360 !?!

Where did MoonlitCoyote go?

We have an outboard motor that is in dire need of being started!